Hyperbranched polymers have been used in the field of manufacturing protective coatings due to its unique structure which leads to the formation of high performance coatings. Hyperbranched polymers have a high number of reactive functional groups exposed at the peripheral edges of the hyperbranched molecule and therefore provide high cross-linking density and high surface protection performance when used in protective coatings.
However, due to the lack of dispersibility of such high molecular weight polymers in water, protective coatings comprising hyperbranched polymers are conventionally provided as organic solvent-based coating systems.
In an age where regulatory requirements are increasingly stricter with regard to volatile organic compounds (“VOC”) emission levels, aqueous-based protective coatings have started to replace solvent-based coating systems in order to reduce the use of organic solvents.
Hence, there have been efforts to increase the dispersibility of high molecular weight polymers in aqueous-based systems.
In known solutions, dendritic polymers are modified by incorporating ionic groups thereon. A known method is by the reaction of hydroxyl functional dendritic polymers with acid anhydrides followed by neutralization of the mixture. In this method, carboxyl groups are grafted onto the peripheral surface of the dendritic polymers to improve its dispersibility in water.
In another known water-based dendritic polymer coating, the coating comprises a fluorine-containing dendritic polymer having at least one pendant fluorocarbon moiety and at least one pendant anionic moiety. Presumably, the presence of the anionic moieties improves the dispersibility of the dendritic polymer in water.
However, it has been observed that the modification of dendritic polymers to incorporate excess ionic groups, for example carboxyl groups, will adversely affect coating performance, especially with respect to the impact resistance, chemical resistance and water resistance of the coating.
Accordingly, there is a need to provide an aqueous-based polymer composition that overcomes, or at least ameliorates, the disadvantages described above.
In particular, there is a need to provide a coating composition capable of achieving dispersibility in an aqueous solvent, and at the same time, capable of providing coatings that exhibit comparable, if not superior, performance when compared with conventional water-based coatings.